Analysis of the Tat-TAR complex from HIV-1 by a number of methods has demonstrated that a key arginine residue in Tat plays the major role in TAR recognition. The synthetic work in this proposal combines this information with results that have shown RNA major-groove selective binding of a series of organic cations. The compounds to be prepared replace different cationic groups on the compounds with guandinium group in an effort to enhance selective recognition of TAR and disrupt Tat-TAR complexes. The ability of the compounds to inhibit tat binding to TAR will be evaluated by gel electrophoresis band-shift methods. A Tat peptide that has been shown to bind specifically to the TAR hairpin will be used in the investigations. A Rev-RRE complex (also using a Rev peptide) will be used to evaluate specificity. Standard methods such as Tm increases and CD spectral changes will be used to directly compare interactions of the compounds with TAR, RRE, and simple RNA duplexes. We will use all of these results to conduct docking experiments of the compounds with NMR derived structures for TAR. Based on the modeling observations, new compounds for synthesis will be designed and synthesized.